When Ohms law applies
Ohms law is a simple relationship for ohmic components where resistance is treated as constant. It is useful for DC circuit examples and quick checks across resistors.
Example
With 12 volts across a 6 ohm resistor, current is 12 / 6 = 2 amperes.
Common mistakes
Use resistance in ohms, not kilo-ohms or mega-ohms unless you convert first. A 6 kOhm resistor is 6,000 ohms, not 6 ohms.
Limitations
Real circuits may involve AC phase, temperature-dependent resistance, semiconductor behavior, source limits, fuses, wiring ratings and safety rules.
Last reviewed: 2026-05-17